1. Field of the Invention
The present invention relates generally to apparatus for use in electrodeposition processes. More particularly, the invention concerns a novel hood construction for use in connection with electroplating tanks for efficiently capturing atoms of the plating materials which may be emitted from the plating solution.
2. Discussion of the Invention
Electrodeposition, or electroplating, is well understood by those skilled in the art and involves forming a layer of metal such as chromium, nickel or copper on an electrically conductive surface such as on an electrically conductive substrate. The principle of electroplating is that the coating metal is deposited from an electrolyte such as an aqueous acid or alkaline solution on to the substrate, i.e., the metal to be coated. The latter forms the cathode (negative electrode), while a plate of the metal to be deposited serves as the anode (positive electrode). A low-voltage direct current is used and the anode is gradually consumed. Various additions are frequently added to the electroplating bath to obtain a smooth and bright metal deposit. These are principally organic compounds, usually colloidal.
Electroplating is widely used in various industries including the automotive, furniture and metal fabricating industries. Component parts, such as automobile crank shafts, cam shafts and like wear parts, metal chair frames, machine tools and the like are routinely plated with chrome and like plating materials in plating apparatus which includes large tanks or vats adapted to receive the electrolyte, the substrate to be plated and the material which is to be deposited, that is the coating metal or electrodeposit.
A major problem in the plating industry is the prevention of contamination of the environment. Strict governmental regulations control the disposal of plating solutions and components, such as filters and fume scrubbers which have been contaminated during the electroplating process. Similarly, emission of contaminates from the plating apparatus into the atmosphere must be strictly controlled. Of particular concern is hexavalent chromium which is used principally inplating wear parts such as crank shafts, cam shafts and the like.
Hexavalent chromium electrolytes require a source of chromium and one or more catalysts in order to plate. The formulation of the traditional process contains hexavalent chromium and sulfate as a catalyst. Proprietary additives can be added to the hexavalent chromium plating bath formulation to enhance particular plating operations or the deposit's properties.
In order to control emissions from plating apparatus, including atoms of the electrodeposit, such as hexavalent chromium and nickel, elaborate ventilation ducting, filtering and scrubbing devices are operably associated with the plating tanks. The emission control apparatus is often large, complex and expensive to manufacture, install and maintain. Further, proper disposal of contaminated components of the emission control apparatus can be difficult and expensive.
Another problem inherent in prior art plating processes, particularly in chrome plating processes, is the efficient removal of hydrogen formed during the plating process. If hydrogen is not effectively removed, the hydrogen will deposit on the surface of the substrate being plated causing surface defects. This problem and a proposed solution thereto is disclosed in U.S. Pat. No. 4,419,194 issued to Angelini.
The apparatus of the present invention provides a simple, efficient and elegant solution to the problem of controlling emissions from the plating tank and for removing hydrogen produced during plating operations. More particularly, the apparatus of the invention efficiently captures the metal atoms released from the plating solution and returns them to the solution in a highly simple manner which totally obviates the need for complex and expensive ducting and fume scrubbing apparatus.
As will be better understood from the discussion which follows, the apparatus of the present invention replaces the complex prior art ducting, fume scrubbing and filtering systems with a unique hood designed that embodies a simple but highly efficient capture means. This unique capture means permits free passage of the hydrogen atoms emitted from the plating solution, but efficiently captures the metal atoms, such as chrome atoms, and returns them by force of gravity to the plating solution. Additionally, the apparatus of the present invention substantially reduces heat loss and eliminates the need to use expensive chemical additives for fume reduction, as for example, an additive sold by Millhorn Chemical of Maywood, Calif. under the trademark "FUMETROL 101". Further, the use of other fume control expedients such as polypropylene balls is avoided.